Equipment preventive maintenance goes wrong most often at the very first decision, which is deciding what goes on the plan at all. Sites either put everything on it, producing a schedule nobody can keep, or put on whatever somebody remembered, producing gaps that are only discovered by a failure. Two questions settle it per item, they take a minute each, and doing them explicitly turns a long list into a short one that a site can actually run every month of the year.
Question one: what does failure cost here
Not what the item costs, what its failure costs. A cheap valve that stops a production line is a high-consequence asset; an expensive unit with a standby beside it may not be. Consequence includes safety, production, occupants and the cost of the emergency response rather than the planned one, and it is the input that should decide how much attention an item gets.
Question two: does the failure give warning
Some failures develop over weeks and announce themselves through noise, heat, vibration or performance. Others happen without notice. Preventive intervals help most where wear accumulates predictably; where a failure is sudden and consequential, the answer is usually redundancy or a spare rather than a shorter interval, and no amount of servicing changes that.
What the two answers give you
High consequence with warning goes on a preventive plan and is a candidate for monitoring. High consequence without warning needs a spare or a standby, plus whatever inspection is genuinely useful. Low consequence with a spare available is a legitimate run to failure. Low consequence without a spare is where sites get surprised, and it is usually the cheapest gap to close. The exercise is also worth doing with somebody from operations in the room, because maintenance and production frequently rank the same asset differently and the disagreement itself is information about what the site actually depends on.
Questions people ask about equipment preventive maintenance
Should every piece of equipment be on the plan?
No, and putting everything on it is the most common cause of a plan being abandoned. A short plan that is actually run beats a complete one that is permanently behind.
Who decides the consequence rating?
The people who would deal with the failure, which usually means maintenance and operations together. Done alone by either, the ratings tend to reflect that group's own inconvenience rather than the site's.
How often should the list be revisited?
Once a year, and whenever the process changes. Equipment moves category when what depends on it changes, and nothing about the equipment itself signals that it has happened.